docs: def _geodetic_to_cartesian(cls, lat, lon, alt):
          """Conversion from latitude, longitude and altitude coordinates to
          cartesian with respect to an ellipsoid
  
          Args:
              lat (float): Latitude in radians
              lon (float): Longitude in radians
              alt (float): Altitude to sea level in meters
  
          Return:
              numpy.array: 3D element (in meters)
          """
          C = Earth.r / np.sqrt(1 - (Earth.e * np.sin(lat)) ** 2)
          S = Earth.r * (1 - Earth.e ** 2) / np.sqrt(1 - (Earth.e * np.sin(lat)) ** 2)
          r_d = (C + alt) * np.cos(lat)
          r_k = (S + alt) * np.sin(lat)
  
          norm = np.sqrt(r_d ** 2 + r_k ** 2)
          return norm * np.array([
              np.cos(lat) * np.cos(lon),
              np.cos(lat) * np.sin(lon),
              np.sin(lat)
          ])